The MPEG-21 is being established as the next generation standard for a multimedia framework by MPEG (Moving Picture Expert Group), which is a Working Group of ISO/IEC JTC 1/SC 29. The goal of MPEG-21 is to realize a multimedia integration framework capable of freely and easily using multimedia contents despite the wide-range characteristics of networks, terminals and users, existing under various environments, by unifying the standards of the existing MPEGs or other standardization groups. The digital item adaptation part of the MPEG-21, Part 7 relates to adaptively transforming the multimedia contents (or digital items) in accordance with the characteristics of networks, terminals (video display devices) and users, the standardization of which is now in progress.
Preceding researches for users with a color vision deficiency are as follows: In “Computerized Simulation of Color Appearance for Dichromats” (Journal of Optical Society of America. A, v.14, no. 10, 1997, 2647-2655), H. Brettel studied an algorithm for allowing common users to experience the color vision characteristics of users with dichromacy. However, in this paper, only an algorithm capable of simulating the color vision characteristics of users with the color vision deficiency is disclosed. An adaptation algorithm for obtaining information that is impossible or difficult to obtain due to the color vision deficiencies is not mentioned. This method requires that contents manufacturers perform a simulation process for dichromats before selecting the colors of the contents. An object of such a method is to avoid a combination of colors that is difficult to be distinguished by the dichromats, if possible, by performing a simulation process to determine whether the dichromats can discriminate the selected combination of the colors.
However, this method urges the contents manufacturers to use limited number of colors, thereby restricting the creativity of the manufacturers and possibly inducing the inconvenience and monotony in the process of recognizing the color information for normal users. Therefore, this method is difficult to satisfy the requirements of various users. Accordingly, there is a need for adaptation not in the contents manufacturing step, but in accordance with individual vision abilities or terminal devices. Nowadays, numerous digital multimedia contents are manufactured even in a day. Thus, such a process performed in the contents manufacturing step has a disadvantage in that it is impossible to adaptively transform the already existing contents.
In order to solve these problems, improving the abilities for recognizing the color information processing of humans with a color vision deficiency by directly transforming the colors of visual contents may be considered. This method has an advantage in that it is not required to redesign a display device and it is possible to adaptively transform all existing contents.
A method of adaptation for users with a color vision deficiency is discussed in “Enhancing Color Representation for Anomalous Trichromats on CRT Monitors Color” (G. Kovacs, Research and Application, v.26 SUPP, 2001, S273-S276), in which an algorithm is disclosed which allows the users to see like a normal user by computing a filter to be mounted in cathode ray tube (to be referred as “CRT”) and applying the obtained filter to a RGB spectrum response value of a corresponding CRT monitor. However, this method applies a filter to a monitor and has a disadvantage in that it is impossible to perform a transformation in accordance with the contents if a plurality of digital items, i.e. a number of images, exist in a screen. Furthermore, it is a burden to purchase a specially manufactured CRT monitor in order to implement this function.
In the Gazette of U.S. Pat. No. 6,362,830, an equation for modeling a human with a color vision deficiency is vaguely derived. However, the process for adaptively transforming visual contents in accordance with the color vision characteristics of humans with a color vision deficiency is very complicated. Moreover, the method does not allow humans with a color vision deficiency to conceive the adaptively transformed visual contents, but allows humans to merely discriminate the visual contents. The disclosure of U.S. Pat. No. 6,362,830 is incorporated herein by reference.
Humans recognize colors and brightness of an object by the visual cells sensing the light reflected from the surface of the object. The visual cells existing in the retina include rod cells and cone cells. The visual cells are specialized cells that function to sense light. Human eyes contain about seven million cone cells and one hundred and thirty million rod cells. Humans discriminate light and darkness using the rod cells and recognize detailed appearance and colors using cone cells. As photochrome contained in the cone cells absorb photons, color recognition of humans is made. Normal humans have three types of cone cells, which absorb different portions of light with a visible wavelength, in the retina. The types are classified into L (long), M (middle) and S (short) in accordance with the peak sensitivity of a wavelength region absorbed by each type of cone cell. Humans recognize colors depending on the ratio of signals which the three types of cone cells generate in accordance with light.
Unlike the above conditions, color vision deficiency is the state in which any of the three types of cone cells does not exist naturally or function abnormally. If there are only two types of cone cells, it is called a dichromacy. In addition, if the function of the cone cells is abnormal, even though all three types exist, it is called an anomalous trichromacy. In the world, about 8% of males and about 0.5% of females have a color vision deficiency. Nevertheless, no method for treating color vision deficiencies exists at present; thus, this study has been commissioned to research a new scheme for treating color vision deficiencies.
It is medically impossible to make humans with a color vision deficiency see original colors. The goal of adaptation for dichromacy is to allow humans with a color vision deficiency to obtain information from the colors of contents at the same level of a normal human, although they are not capable of seeing the original colors.